GPC ram cassette

	A	B	C	D	E	F	G
1	U6 (74ACT139 dual 1-of-4 decoder)
2	Pin #	Name	From/To	Part	Pin #	Name
3	1	/Ea	from	cart	49	/ROMSEL
4	2	A0a	from	CL1 (jumper)	1M/2M/4M config jumpers
5	3	A1a	from	CL2 (jumper)	1M/2M/4M config jumpers
6	4	/O0a	to	U1 (SRAM)	22	/CE1
7	5	/O1a	to	U2 (SRAM)	22	/CE1
8	6	/O2a	to	U3 (SRAM)	22	/CE1
9	7	/O3a	to	U4 (SRAM)	22	/CE1
10	8	GND
11	9	/O3b	to	U1-U4 (SRAM)	29	R/W
12	10	/O2b
13	11	/O1b
14	12	/O0b
15	13	A1b	from	U8 (counter)	12	MAX/MIN	13 and 14 can be connected via jumper CL5
16	14	A0b	from	U11 (multivibrator)	13	Q1	(to disable write protection)
17	15	/Eb	from	cart	54	/WR
18	16	Vcc
19
20	U8 (74LS191 4-bit counter)
21	Pin #	Name	From/To	Part	Pin #	Name
22	1	Db	GND
23	2	Qb
24	3	Qa
25	4	/EN	from	U9 (decoder)	7	/O7
26	5	DOWN/UP	GND
27	6	Qc
28	7	Qd
29	8	GND
30	9	Dd	GND
31	10	Dc	GND
32	11	/LOAD	from	U11 (multivibrator)	13	Q1
33	12	MAX/MIN	to	U6 (decoder)	13	A1b
34	13	/RCLK
35	14	CLK	from	cart	54	/WR
36	15	Da	GND
37	16	Vcc
38
39	U9 (74ACT138 1-of-8 decoder)
40	Pin #	Name	From/To	Part	Pin #	Name
41	1	A0	from	cart	38	A13
42	2	A1	from	cart	39	A14
43	3	A2	from	cart	46	A21
44	4	/E1	from	cart	48	A23
45	5	/E2	from	cart	47	A22
46	6	E3	from	U11 (multivibrator)	13	Q1
47	7	/O7	to	U8 (counter)	4	/EN	write to $206xxx 15 times to enable write
48	8	GND					and a 16th time to disable again
49	9	/O6
50	10	/O5
51	11	/O4
52	12	/O3
53	13	/O2
54	14	/O1
55	15	/O0
56	16	Vcc
57
58	U11 (74LS123 dual monostable multivibrator)
59	Pin #	Name	From/To	Part	Pin #	Name
60	1	A1	GND
61	2	B1	from	cart	1	MCK
62	3	/CLR1	from	cart	26	/RESET
63	4	/Q1
64	5	Q2
65	6	Cext2
66	7	RCext2
67	8	GND
68	9	A2
69	10	B2
70	11	/CLR2
71	12	/Q2
72	13	Q1	to	U9 (decoder) U6 (decoder) U8 (counter) U1-U4 (SRAM)	13 14 11 30	E3 A0b /LOAD CE2
73	14	Cext1
74	15	RCext1
75	16	Vcc
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